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In today’s world, there are many different protocols, and some are better equipped to work in different applications. Modbus and profibus each have strengths, and there is some overlap as to what each of them is capable of. Some people, however, consistently prefer to use modbus over profibus.

Modbus was originally designed in the mid 70’s and was a proprietary protocol for Modicon. The company published it royalty free before finally making it an open protocol. Many companies began using it, and because of this, there are now several variations. Even though it has variants, it is best described as simple. It’s easy to implement and easy to use. This is one of its biggest strengths. The specification document is less than 100 pages, which indicates its simplicity. Modbus usually refers to one of three protocols – Modbus ASCII, Modbus RTU, or Modbus TCP/IP.

Modbus ASCII was the first modbus, and usually runs on the RS-232 or the RS-485 physical layer. There is one master and all slaves are polled on demand by the master. The message frame can be up to 253 bytes.
Modbus RTU is a variation of Modbus ASCII. The difference is the encoding of the data. RTU uses bytes to encode messages, which increases the throughput.
Modbus TCP/IP was added much later, and can be thought of as, essentially, a way of encapsulating an RTU packet within a TCP/IP packet. It’s simple to use, but is slower than other Ethernet products. It is still adequate for monitoring applications.

As Modbus is a simple master slave protocol, and the master has full control of the communication. The slave will only respond when asked. The master will record the outputs, and read the inputs from every slave during every cycle. The slave devices don’t join the network, and they only respond when spoken to, and remain idle when they are not being spoken to. There’s no requirement for a watchdog timer, and there’s no requirement for diagnostics for the slave’s health.

Modbus usually uses the RS232 or the RS485 physical layer, but it can also use other physical layers, like phone lines, or wireless. RS232 and RS485 were established physical layers during the Modbus original development, and it didn’t add any new requirements.

In the case of using phone lines and wireless, Modbus has excelled. Phone lines and wireless introduce delays in the messages, which can be problems, but Modbus either deals with this, or it adapts to work in these applications.

Modbus can be used from a controller, or monitor to a smart device, controller, or monitor to a smart device from multiple vendors and for remote monitoring of information from a smart device.

Profibus is not only more complicated to implement and use, but it also uses specialized characteristics which tie it to RS485. RS485 is used in many different industries but it will become obsolete. Modbus, on the other hand, is always going to grow and be utilized because of its simplicity, and because it can be adjusted to the Ethernet, without overly complicated processes.

However, it is possible to utilize both protocols to work together. Modbus is the data transport between a master controller/data concentrator and has a remote profibus station. Using both protocols allows the simple implementation and easy modem support of modbus, while also gaining some positives from profibus. Profibus can be used in hazardous and multi vendor applications, and modbus provides a link between a SCADA system and a data concentrator.

This is a digital computer which is specially adapted for the control of manufacturing processes such as assembly lines, lighting fixtures, robotic devices, amusement rides or activities that require high-reliability control, process fault diagnosis and ease of programming.

Programmable Logic Controllers (PLCs) have progressively become a fundamental part of the industrial environment. It is imperative to understand their basic functionalities as a technician involved with PLCs controlled processes.

PLCs are designed for multiple arrangements of input and output, resistance to impact and vibration, electrical noise immunity and extended temperature ranges. The programs are written on a computer and then downloaded to the PLC. The Programs to control machine operation are stored either in non-volatile memory or battery backed up RAM. A PLC allows for output results in response to input conditions within a set time.

A brief history of the PLC

Before the PLC, sequencing and control for manufacturing were composed of drum sequences, relays, and closed-loop controllers. The process of updating these was expensive and time-consuming because it required individual rewiring of relays.

PLCs were invented to replace the rewiring of relay based control panels in the American automotive industry when there was a change in production models.

GM Hydramatic, which is General Motors automatic transmission division, issued a request in 1968 for the hard-wires relays systems to be replaced. Bedford Associates of Bedford, Massachusetts gave the winning proposal.

Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product which they named MODICON (MOdular DIgital CONtroller). One of the very first 084 models built was decommissioned after almost twenty years of nonstop service. The automotive industry remains one of the largest users of PLCs to date.

Previously, the sequencing and control for automobiles manufacturing relied on hundreds of relays, dedicated closed-loop controllers, drum sequencers, and cam timers. Updating such facilities was costly and time-consuming, as technicians needed to manually and individually rewire the relays.

When digital computers were invented, they were used in in industrial processes to control combinatorial and sequential logic due to their general-purpose programmable devices. However, these early computers required programming specialists as well as rigorous operating environmental control for cleanliness, temperature and power quality. To overcome these challenges, the PLC was developed with several key attributes. It would tolerate a harsh environment; effortlessly support discrete input and output. Also, its operations could be monitored and would not require years of training to use.

Advantages of PLCs

Reduced Cost: PLC prices range from a few hundred to a few thousand. PLCs are cost efficient because they eliminate shipping and installation costs.

Flexibility: A single PLC can effortlessly run many machines.

Ease of Troubleshooting: With PLC control, any changes in sequence or circuit design are as simple as retyping the logic. PLCs allow for a fast and cost effective way of correcting errors. Moreover, a PLC program can be tested after it is developed before it is implemented in the field.

Visual observation: PLCs have a visual display on a screen which makes troubleshooting simple and fast.

Components of a PLC

All PLCs have the similar basic components. These include controller relay units for input and output, timers, CPU, a peripheral device, communication processor (CP), interface module (IM) and power supply. These components work jointly to carry information into the PLC, evaluate that information after which the information is sent back out to various fields.

Modbus RTU and Modbus TCP/IP are usually communication protocols. The communication protocol is the system of rules, which permit two or more entities to package and transmit data, and are implemented in software and hardware. Networking of industrial devices like level sensors to a PLC and pressure transducers is achieved by using a kind of communication protocol referred to as Fieldbus. Modbus is a widely used Fieldbus, which supports two-way communication for a remote operation like set-up and programming and permits transferring lots.

TCP/IP and RTU are two popular types of Modbus. Basically, these are two different methods of data transmission. While the way structured data for transmission is defined by Modbus, wrapping the data structured for specific ways of transmission is defined by TCP/IP and RTU.

Modbus RTU

A network of field devices that use serial communication is known as Modbus RTU. You can interconnect Modbus devices and sensors in a network.

RTU is widely used for industrial control networks because it has been in existence for long around, and it is supported by lots of software and hardware.

Modbus TCP/IP

The creation of Modbus TCP/IP came about so as to maximize the benefits of an Ethernet network. Essentially, Modbus RTU that uses the TCP interface in an Ethernet network is what is called Modbus TCP/IP. The structure of Modbus data is defined with the use of the application layer applied in the TCP/IP protocol. The TCP is utilized to make sure data is received and sent the right way, and the address and routing information is described as IP.

Basically, the Modbus TCP/IP command is a Modbus RTU command, which is included in an Ethernet TCP/IP wrapper.

The advantage of using Modbus TCP/IP is with the use of the existing Ethernet network equipment, which is inexpensive and widely available.

Generally, TCP/IP and RTU exist to help you transmit data in a manner which is comfortable and inexpensive for you. Contact us today us to talk about your particular application, and assist you in determining the best way to transmit data.

The Difference Between ControlNet and DeviceNet

When it comes to connecting floor-factory devices in a cost effective way, DeviceNet is a communication network that is open and effective. These floor factory devices include push buttons, sensors motor starters and drives as well as control systems that deliver data at fairly good speeds of approximately 125 to 500kbits/s making it the leading market device for networking. DeviceNet is also efficient for simple devices, since the length of its messages that often exchange range from about 0 to 8 bites. Additionally, in the case of sending longer messages, there is message fragmentation that makes it possible for the data to be availed in numerous packages.

DeviceNet has a clear market spot with device level communication since there is no other kind of network that has the capability to transfer controlled data and information in small packages that are also pocket-friendly. There is a considerable cost barrier when it comes to implementing IP/ Ethernet at the device level since DeviceNet, uses a cable configuration with a multi-drop. The multi-drop can allow you to connect up to 50 devices on a single cable. A switch (point-to-point) configuration is needed for Ethernet to be functional for control applications. There are up to 50 wires that run between the devices and the switch. TheDeviceNet design is common in several companies with high volume automotive production. The design is known as CAN and it is simple without the need for memory in its controller or device. This ensures a cheap outcome component that is as low as $1 and is available from various chip manufacturers. Additionally, the CPU may only need to have the CAN protocol without any additional components of communication, hence, making it rather easy and cheap to use commercially for profitable products and systems.

The Newest Mode of Transportation- Ethernet/ IP

ControlNet International published and accepted the layer application that was shared by both DeviceNet and ControlNet over Ethernet in the spring of 1998 when ControlNet applied CIP. The standard Ethernet/ IP was introduced by ControlNet International as well as other open network organizations. Ethernet users enjoyed information and control services from the open application layer.

What are the differences between the new EtherNet/ IP and the Ethernet that has been around for over 20 years?

To begin with, the major difference is that a common language must be met so as to choose products from various vendors so that they could operate hand-in-hand on the plant floor. For the last ten years, there have been several vendors who have been applying their layer of Ethernet products that have been presented to the market. Consequently, the data sent by vendor A’s product is not comprehensible by vendor B’s Ethernet product. However, when trying to take advantage of the current rich, analytical products this is not the ultimate circumstance one would like to be in.

Additionally, Ethernet/ IP gives its users the ability to control the network, acquire data diagnose capabilities as well as configure the device. It uses the TCP/IP protocol that is standard, therefore, controlling the messages and permitting information.

The commercial component availability, current architecture, and the experience of the users has led to the evolution of Ethernet/ IP. It is essential to consider the cost of the devices in that the commercial Ethernet PC card costs only $20 while the industrial controller may be more than $1,000. The Central Processing Unit and the memory are necessary in the module in order to perform the tasks of the PC, hence the difference of the costs. Also, the industrial products are made to resist increased levels of humidity, temperatures, shock, vibration, as well as electric interference as compared to the products sold off-the-shelf.

The reduced pricing of Ethernet might be connected to the training and manpower needed making it a preferable device for several IT and IS departments for many years. The extensive exposure to the Ethernet technology has led to expansive knowledge as well as unmatched resources. Besides being fast, it has a significantly high data transfer rate as compared to other networks.

Real-Time Control Using ControlNet

Why is ControlNet a common selection yet users can still have real-time control with Ethernet? It is because ControlNet offers a faster link and can handle complicated control systems such as weld control, coordinated drive systems, vision systems, complex batch control systems, motion control as well as the process control systems. This is because it has huge data requirements, and multiple controller systems and human machine interfaces. It also has the best system with multiple controllers joining all the different controllers such as PCs, robots, and welders.

ControlNet users are loyal to it because it can handle control systems that are complicated by the presence of passive taps making the network unpowered. The passive taps ensure that a loss of any of the nodes will not lead to network failure. On the losing side, Ethernet has powered switches meaning that loss of power will result in loss of network. For this reason, users will opt for ControlNet to ensure extensive media redundancy, cabling options that are safe and other features related to ControlNet.

The applicants of ControlNet would want the following advantages:

Multi-Media Options

Complete solution for product availability

Engineering Productivity with Deterministic Performance

System uptime with Media Severance

Designed Safe cabling for Process Control

Engineering Productivity with Deterministic Performance

The configuration software of ControlNet assists in eradicating any clashes within the configuration and errors in the device by monitoring the usage of the network bandwidth as well as the communication rates of the device by notifying users in case hitches come up. The additional software is helpful in that; Users can configure a sensor that is updated every 5ms as well as drives to update every 10ms and make confirmation that there is enough bandwidth. The sensor and the drive are updated as programmed without network interruption from activities that use the network such as messaging and configuration.

Complete Solution from Product Availability

The advancements of ControlNet and the customer requirements ensure that the clients can choose from a wide variety of products. At www.controlnet.org, there is an exclusive list of products from ControlNet International and it keeps growing in number and variety of its choices.

System Uptime with Media Severance

Physical media redundancy is standardly offered by ControlNet. There is the assurance of extra security against a cable being damaged or cut. On execution, each device has a connection to two cables and the same data is transmitted parallel on each cable. In the case that either of the cables is not functioning but the operation continues uninterrupted without the loss of communication, the alarms are sent to the management system without manual intervention.

Designed Safe Cabling for Process Control

ControlNet offers naturally safe cabling options because of its design with passive network components that can be used in dangerous situations such as I/O and other components. Additionally, fiber optic cabling makes use of barriers that segregate dangerous areas. Using ControlNet as well as the design of the system offers a cost-effective system that is relatively simple.

Multiple Media Options

ControlNet offers flexibility with its cabling components that are used when designing an application. The trunk cable is available in optical and coaxial fiber and makes up the central backbone of the system. The users use their environments to pick out the most suitable media. Also, there are special cables used that are flexible with special insulation material and much more. In order to connect devices and gaps to the networks, a BNC connector is used. The fiber and coaxial repeaters extend the length and create a ring, star or tree configuration.

Have you chosen the Right Bus?

When looking for an effective way of transferring data from a device to the internet, it is important to select the best means of transportation. Many travelers and plant managers enjoy the freedom of choosing between a variety of travel options such as planes, buses, and trains among others. All the same, you are the one who knows the best network for your application and whether it would be DeviceNet, ControlNet, Ethernet/ IP or a blend of all these networks.

The Modbus TCP/IP, or Modbus-TCP is similar to the Modbus RTU protocol, but with a TCP interface that runs on Ethernet. The Modbus messaging structure is an application protocol that rules the organization and interpretation of data independently of the data transmission medium.

TCP refers to the Transmission Control Protocol, while IP refers to Internet Protocol. These two protocols are the transmission medium for the Modbus TCP/IP messaging. Essentially, the Modbus TCP/IP exchanges blocks of binary data between computers. This protocol is also considered to be a world wide standard and provides a foundation for the World Wide Web. The TCP is to ensure all the packets of data are received correctly, with the IP ensuring that the messages are addressed and routed correctly. This TCP/IP combination is the transport protocol, it is the Modbus application protocol that defines what the data means, and how it is interpreted.

To summarize, the Modbus TCP/IP uses Ethernet and TCP/IP to transport Modbus message structure data between compatible devices. What this means, in essence, is that it combines the physical network of the Ethernet, with the TCP/IP networking standard and the Modbus application protocol as a standard of data representation. So, it is a Modbus communication with an Ethernet TCP/IP wrapper.

The Modbus and user data are contained in a TCP/IP telegram, but are not modified at all. The Modbus error checking field, checksum, isn’t used. The standard Ethernet TCP/IP layer checksum methods are utilized instead to guarantee the integrity of the data. The Modbus frame address field is replaced by the unit identifier in Modbus TCP/IP, and is part of the Modbus application protocol header.

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When configuring a DH+ link for your system it’s important to consider the following application guidelines.

To achieve acceptable response times, you will need to minimize the number of DH+ nodes. It’s important when minimizing DH+ nodes to keep frequency and size of the messages exchanged between devices in mind.

To achieve the fastest control response time possible, you’ll need to limit the number of stations on your overall network. To bring on additional stations, establish separate DH+ networks.

Never remove or add stations to the network during process or machine operation. If the network token is situated with the removed device, it can be lost to the rest of the network. Automatic re-establishment of the network could take several seconds to activate. During this time, control is interrupted or unreliable.

Try to avoid programming controllers as much as possible online during process or machine operation. This could increase response time by possible long bursts in DH+ activity.

Add a separate DH+ link where possible for processor programming to keep the effect of programmed terminals from the process DH+ link.

With the increase in demand for industries to manufacture and produce top quality products, it’s important that the technology and industrial automation services behind the company is sound to ensure smooth operation of the business each and every time. Automation engineering technology is used by many industries to produce an abundance of items ready for market and resale, amongst other things. But what exactly is automation engineering technology you ask? The following is a brief guide to what this technology is so you can be more informed.

What Is Industrial Automation Engineering Technology?

Automation engineering technology is the term that’s used for a variety of systems which include process controls and communications. Technicians in the industrial automation engineering field generally combine key fundamental principles of mechanical engineering technology with electronic and electrical circuits to develop, design, test, and manufacture computer controlled and electrical mechanical systems which are becoming a key foundation element in industrial industries.

The industry of automation is a branch of the electronics field and is fast becoming one of the major growing areas of international and national high technology economies. Industrial automation engineering technology features a combination of electronics, mechanics, and electrical, and includes the control or interaction of computers, motors, hydraulics, pneumatics, and other processes which are applied and used within manufacturing.

What Do Automation Engineering Technicians Do?

Industrial Automation engineering technicians use theories and principles of engineering, science, and mathematics to come up with solutions to technical problems in areas of development, research, inspection, construction, manufacturing, and maintenance. More practically orientated than most engineers and scientists, automation engineering technicians general assist in the research and development process of ordinary scientists and engineers.

The areas where automation engineering technology is used includes in quality control environments. This means the inspection of processes and products, along with the process of collecting data and conducting test. In the area of manufacturing, technology is used to help with the product development and design, along with the production process. Programmable logic controllers or PLCs are a significant area where automation engineering technology is used. This involves conducting work with special-purpose computers to create synchronization of the different technologies which are used within the manufacturing process. Automation engineers who are familiar with PLCs generally setup and use the special-purpose computers.

Conclusion

Automation engineering technology plays a major role in many businesses and industries. If you’re a business that requires an automation engineering technician it’s best to check their credentials and ask them questions about what they can help you with to make sure you find the right technician to suit your individual needs.

Understanding the differences between Modbus and Modbus Plus are very important. Modbus is based on the RS232C serial standard communications that define the cabling, connector pinouts, signal levels, parity checking, and transmission baud rates. It’s a master slave protocol that uses the Modicon controllers through a common language.

Modbus Plus, is a network protocol that uses high speeds between the networks of peer connections. Upon the receipt of the token frame, Modbus Plus nodes on the access of the network. When the node hold a token, it can start transactions with several devices on the same network.

Developed in 1979, Modbus industrial serial protocol makes communication between automation devices possible. It is used with programmable logic controllers or PLCs. It transmits the information over serial lines that exist between electronic devices. The Modbus Master requests the information and the device that supplies the information are the Modbus Slaves. In a standard network, there are up to 247 slaves and one master. Each of the slaves have their own unique addresses. The master has the ability to write information the each of the slaves. The slave device has to wait to be asked for information and cannot give it without permission. The master writes the data to a slave devices registers and also reads the data from the registers.

What Modbus is used for?

This common protocol is used by many devices for efficient, reliable, and simple over many of the modern networks. A giant server can be used as the master for a PLC and then the PLC can be used as a valve, motor, sensor, or other device that is embedded. It is now the standard in the industry when it comes to communications protocol and the most available way to connect industrial electronic devices. Many manufacturer’s use it in various industries. It is mostly used to give off signals from control devices and instrumentation back to system gathering data or main controller. An example could be a system that tells the humidity or temperature back to a computer. A remote terminal unit or RTU within a supervisory control and data acquisition or SCADA system can be connected to a Modbus.

Modbus/TCP can make the definition of slave and master less obvious. That is because the Ethernet can allow for a communication system that works as a peer to peer connection. The client and the server are better known in Ethernet-based networking. When this happens, the slave can become the server and the master can become the client. That allows for more than one client to obtain data from the server. That way there is a chance of having multiple masters and multiple slaves. It allows for a system where the slave and the master are not defined on a physical device.

How does Modbus work?

Serial lines transmit the Modbus between devices. In a simple setup, there is a single serial cable that is connected to two serial posts, the master and the slave. Then the data is sent in bits, which are a series of ones and zeros. They are sent as a voltage. The zeros are positive volts and the ones are negative volts. These bits very quickly sent at a speed of 9600 bits per second called a baud.

Popular terms to know

When dealing with a Modbus communication protocol, you will want to know some popular terms. They will help you understand the concepts better.

Hexadecimal: Every block of eight bits which is called a byte. It can be represented by pairs of 256 characters from 00 to FF. Long strings of zeros and ones can be difficult to read. The bits are shown and combined in hexadecimal. Each of the block of four bits are represented by one of the sixteen characters ranging from 0 to F.

ASCII: It stands for American Standard Code for Information Interchange. Every eight bits can be represented and combined by one of the 256 ASCII characters just like every 4 bits can be represented and combined by one of the sixteen hexadecimal characters from zero to F.

How is the data stored in a Standard Modbus?

The information is stored in four tables in the slave devices. Two of these tables store the on and off values or coils and two store the numerical values or registers. The registers and coils have a read-write table and a read-only table.

Every table has 9999 values

Every contact or coil is one bit. Plus, it is assigned an address between 0000 and 270E

Every register is one word that equals 16 bits which equals two bytes. They have a data address between 0000 and 270E.

Coil and register numbers are thought of as location names that do not appear in the message.

What is a Slave ID?

Every slave in the network gets a unique unit address that is between 1 and 247. When there is data requested from the master, the slave address is the first byte that is sent. The reason why it does that is to tell the master whether to ignore the message or not.

What is the function code?

The master sends the second byte as the function code. It is the number that tells the slave what table to access and if it should write to or read from the table.

What is a Cyclic Redundancy Check or CRC?

The two bytes that are added at the end of the Modbus message designed for error detection. All of the bytes in the message are used to calculate the CRC. The device that is receiving the message calculates the CRC and then it compares it to the sending device’s CRC. It is used for protection. If even one part of the message is incorrectly received, the CRC is different and then the error will result.

What is word and byte ordering?

The way the data is stored in the registers is not defined with the Modbus specification. So, some manufactures have implemented Modbus into their equipment that stores and transmits a higher byte first and then a lower byte next. Other devices transmit and store the lower byte first.

The technology is forever changing and improving. The new methods make it easier for communication between master and slave.

With each new era, there comes new IT issues and manufacturing trends to deal with. The most popular topics that have been featured in many manufacturing publications include:

The Internet of Things

Big Data

Cloud Computing

These trending topics involve devices that are networked together and have a lot of data available to do things. Also, they include a decision on whether the applications are accessed and the data is stored on a server or your computer.

However, there are supporting technologies that work behind them all that have already been developed. Here is what you need to know about each of these topics to manage through them.

The Internet of Things or Connected Industrial Devices

The Internet of Things involves a lot of devices that are industrial that are networked together. This could be plants with thousands of devices that are networked together.

Reasons to network:

Everything can be managed from anywhere

Reduced hardware costs and complexity because of a the one network

Information and control can be moved when needed

The whole point of the Internet of Things is to connect industrial devices to each other so that the connectivity can be used to improve business.

Challenges to network:

Learning and understanding the new technology

Deciding how to design the systems

With the development of this concept, the vendors and groups that set standards will take care of the difficult parts. The evolution of the technology will handle the growth as more wireless ports are added. Security will be upgraded helping with the management of higher traffic levels. Then, more IP addresses are created finalizing the process of continuing the business environment prior to the growth. Plus, your company has to encourage the use of this innovative technology.

Big Data

When data sets are incredibly complex and large that the regular applications for data processing are inadequate, this is referred to as Big Data. There is a lot of information that can be used for many different things, but isn’t being used. New software is now used that can analyze the large amounts of data, so that it can be used. Web companies and search engines use this type of technology. The systems measure, record, and interpret the information. For example, Amazon, makes suggestions to their customers about what to buy based on the information that is gathered from past purchases and items that the customers put in their cart. They make suggestions for repeat purchases and send notifications when the price on items that are saved in their cart changes. This is done to initiate a response from the customer to buy some more cologne or buy the tablet that just dropped in price.

Once a company learns how to utilize the data, they are able to build their business and offer more products that the consumers will want.

3.Cloud Computing

Cloud computing deals with the computation and storage of your data on another source and not on your computer. Today, the computing power isn’t completely viable for use in an industrial capacity. However, the storage capacity is very strong. It provides a great way to share your data and back up your files.

Gateways can also segment networks into logical segments. They can allow for a clear division for different parts of the facility. If there is a need to optimize performance or maximize availability, the portal’s division can be useful.Industrial gateways allow you to optimize your network whenever your goal is to redesign, configure, or extend an industrial network.